1. Field
The present invention is directed to an exposure indicating device.
2. Related Art
A variety of respirator systems exist to protect users from exposure to dangerous chemicals. Examples of these systems include negative pressure or powered air respirators which use a cartridge containing a sorbent material for removing harmful substances from the ambient air, and supplied air respirators.
A number of protocols have been developed to evaluate the air being delivered to the user. These protocols may also be used to determine whether the sorbent material is near depletion. The protocols include sensory warning, administrative control, passive indicators, and active indicators.
For example, an end-of-life sensor (“EOLS”) or end-of-service-life indicator (“ESLI”) can warn that a filter element in such a device may be approaching saturation or may be ineffective against a particular material. Patents and applications relating to personal protection or respiratory protection (and in some instances to sensors or indicators in general or to EOLSs or ESLIs in particular) include U.S. Pat. No. 1,537,519 (Yablick), U.S. Pat. No. 3,966,440 (Roberts), U.S. Pat. No. 4,146,887 (Magnante), U.S. Pat. No. 4,154,586 (Jones et al.), U.S. Pat. No. 4,155,358 (McAllister et al.), U.S. Pat. No. 4,326,514 (Eian), U.S. Pat. No. 4,421,719 (Burleigh), U.S. Pat. No. 4,530,706 (Jones), U.S. Pat. No. 4,597,942 (Meathrel), U.S. Pat. No. 4,684,380 (Leichnitz), U.S. Pat. No. 4,847,594 (Stetter), U.S. Pat. No. 5,297,544 (May et al.), U.S. Pat. No. 5,323,774 (Fehlauer), U.S. Pat. No. 5,376,554 (Vo-Dinh), U.S. Pat. No. 5,512,882 (Stetter et al.), U.S. Pat. No. 5,666,949 (Debe et al. '949), U.S. Pat. No. 5,659,296 (Debe et al. '296), U.S. Pat. No. 6,375,725 B1 (Bernard et al.), U.S. Pat. No. 6,497,756 B1 (Curado et al.) and U.S. Pat. No. 6,701,864 B2 (Watson, Jr. et al.); US. Patent Application Publication Nos. US 2004/0135684 A1 (Steinthal et al.), US 2004/0189982 A1 (Galarneau et al.) US 2004/0223876 A1 (Kirollos et al.) and US 2005/0188749 A1 (Custer et al.); and PCT Published Patent Application No. WO 2004/057314 A2.
Other patents and patent applications relating to sensors or indicators but not to EOLSs or ESLIs include U.S. Pat. No. 5,611,998 (Aussenegg et al.), U.S. Pat. No. 5,783,836 (Liu et al.), U.S. Pat. No. 6,007,904 (Schwotzer et al.), U.S. Pat. No. 6,130,748 (Krüger et al.) and U.S. Pat. No. 6,248,539 (Ghadiri et al.); U.S. Patent Application Publication No. US 2004/0184948 A1 (Rakow et al.); and US Statutory Invention Registration No. H1470 (Ewing et al.).